In the display technology field, touch screens have been applied more and more widely as new input devices.
Depending on touch input ways, touch screens include resistive, capacitive, optical, sound wave and electromagnetic types. Capacitive touch panels have advantages of fast response time, high reliability and high durability. According to the integration modes with display devices, touch screens are classified into at least in-cell and add-on types.
For a structure of a touch screen, it is generally to form touch driving electrodes and touch sensing electrodes for realizing touch function in a touch area. At present, a multipoint touch-type touch screen is based on the coupling capacitance (namely mutual capacitance Cm) at intersections of touch driving electrodes and touch sensing electrodes and determines the location of a touch point by the change of the magnitude of coupling capacitance when a finger touches the touch screen.
At present, signal delay of touch driving electrodes and touch sensing electrodes has become one of the key factors that limit large size touch screens. Specifically, signal delay time T is mainly determined by RC in which R is resistance of touch driving electrode and touch sensing electrode, and C is the coupling capacitance Cm and the parasitic capacitance. If the signal delay is large, it will severely influence touch effect of a touch screen, such as the touch accuracy and sensitivity. The problem of signal delay is severe in large size touch screens.
At present, in order to not influence the display effect, most touch screens use transparent electrodes for touch driving electrodes and touch sensing electrodes, for example, using metal oxide film layer or carbon nano materials for touch driving electrodes and touch sensing electrodes. The metal oxide film layer or carbon nano material has high resistivity and large signal delay T=RC occurs, and therefore the touch effect is poor. Particularly for large size touch screens, the touch effect is even more poor due to signal delay.